This electrocardiogram shows diffuse, pronounced ST segment depression, which may reflect either subendocardial injury or profound diffuse ischemia. Often, true subendocardial injury is associated with elevated cardiac biomarkers that define a non-ST elevation myocardial infarction. If serum levels of cardiac biomarkers are not elevated, the constellation of findings is consisted with unstable angina pectoris. The characteristic feature demonstrated here is the ST segment depression seen in most leads.